This invention relates to a parting or grooving insert.
Such parting or grooving inserts of the kind to which the present invention particularly relates are formed with a front cutting edge which is inclined with respect to a normal to a longitudinal median plane of the insert by an angle known as the lead angle of the insert. Such inserts are generally divided into three categories, namely right-hand and left-hand inserts depending on the direction of inclination of the insert and neutral inserts where the leading angle is substantially zero.
It is known to provide double-ended indexable inserts having a central body portion and a pair of opposite cutting end portions. Such inserts are designed to be releasably retained between a pair of clamping jaws formed in an insert holder so that one operational cutting end portion is, at any particular time disposed so as to extend beyond the holder whilst the other non-operational insert is retained within the holder. In order to ensure an effective constant positioning of the insert within the holder and, in consequence of the operational cutting edge, it is generally arranged that the holder is formed with a support surface which is abutted by the rear non-operational end of the insert and in this way it is ensured that in operation the insert is always held in a predetermined position.
With such known double-ended inserts the cutting edge is formed at the intersection of an upper rake surface of the insert and a front relief flank thereof. Where with right-handed or left-handed inserts the cutting end portion is formed with a leading angle the relief flank is correspondingly inclined with respect to a normal to a longitudinal median plane of the insert. In consequence, when the insert is fully mounted in the holder the rear end thereof abuts the holder""s supporting surface via an edge portion of the relief flank rather than by way of surface-to-surface abutment. It will be readily appreciated that such an edge-to-surface abutment gives rise to an instability of mounting of the insert in the holder. It will furthermore be realized that, if the support surface of the holder were formed to be similarly inclined to the relief flank so that an effective surface-to-surface abutment of the insert and the support surface would be achieved, differing holders having differingly inclined support surfaces would have to be provided for right-hand and left-hand inserts.
It is an object of the present invention to provide a new and improved double-ended cutting insert wherein the above-referred to disadvantages are substantially reduced or avoided.
According to the present invention there is provided a double-ended parting or grooving insert comprising a central body portion and a pair of opposite cutting end portions; each cutting end portion having an upper rake surface and front and side relief flanks and a front cutting edge formed at an intersection of said rake surface and said front relief flank; characterized in that said front relief flank comprises an upper relief flank surface component; a lower abutment surface component inset with respect to said upper component and disposed substantially normally with respect to a longitudinal median plane intersecting said front cutting edges and an intermediate surface serving to bridge said upper and lower components.
Preferably said cutting edge and said upper relief flank surface are inclined with respect to a normal to said plane by a leading angle of said cutting edge.
Thus, the double-ended parting or grooving insert in accordance with the invention can be either of the neutral type where the front cutting edge and the associated upper relief flank surface have a zero leading angle or of the right-hand or left-hand type where the front cutting edge and the associated upper relief flank surface have leading angles of respectively opposite senses. In all cases, however, the cutting insert can be securely retained in an appropriate insert holder with its abutment surface abutting over its entire surface area the adjacent support surface of the holder. In this way the same insert holder can be effectively used irrespective of whether the insert is neutral, right-handed or left-handed and at the same time ensure the effective supportive abutment of the insert within the holder.